Question

What number should be added to the expression x2 + 4x to change it into a perfect square trinomial?

Answer 1

Ax^2+bx+x=0 so divide it by two
 x^2+4x+4(b=4, 4/2 is 2 and 2^2 is 4 that's the number

Answer 2

4. Then you have x^2+4x+4 which gives you (x+2)(x+2) when you factor it.